Post processing of iris images to increase image quality

Abstract

A rapid iris acquisition, tracking, and imaging system can be used at longer standoff distances and over larger capture volumes, without the active cooperation of subjects. Light illuminates the subjects' eyes and a high resolution camera captures images of the irises. The images of the irises are processed by a post processing module to improve their quality. In one approach, the point spread function of the image capture subsystem is estimated using glint reflections from the eye, and the estimated point spread function is used in deconvolution to increase the resolution of the iris images. The post processed iris images have sufficient resolution to be used for biometric identification.

Description

CROSS-REFERENCE TO RELATED APPLICATION(S)[0001]This application claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Patent Application Ser. No. 60 / 803,006, filed May 23, 2006, which is a continuation-in-part of U.S. patent application Ser. No. 11 / 297,578, filed on Dec. 7, 2005, entitled “Iris Imaging Using Reflection From The Eye,” which claims priority under 35 U.S.C. §119(e) to both U.S. Provisional Patent Application Ser. No. 60 / 654,638, “Biometric Identification and Iris Imaging Using Retinal Retro-Reflection,” filed Feb. 17, 2005, and U.S. Provisional Patent Application Ser. No. 60 / 634,331, “Adaptive Optics (AO) Imaging Applied to Biometric Identification Using Iris Imaging,” filed Dec. 7, 2004. The subject matter of all of the foregoing is incorporated herein by reference in their entirety.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]This invention relates to imaging of the human iris, as may be used for biometric identification. More specifically, ...

AI Technical Summary

Benefits of technology

[0011]Embodiments of the present invention include iris imaging systems that use post-processing to increase the quality of captured iris images, such as resolution, contrast or noise characteristics. In one aspect, an iris imaging system captures lower resolution images and an image post processing module increases the resolution of the images. As a result, the iris imaging system can be used at longer standoff distances and / or over larger capture volumes, without the active cooperation of subjects.

[0012]In one embodiment, light illuminates the subjects' eyes. Reflection from the eyes (e.g., retro-reflection from the retina or glint reflection from the cornea) is used to steer (and preferably also focus) a camera to the eyes in order to capture images of the irises. The captured iris images are post processed by the imaging system to improve the quality of the images, making them suitable for biometric identification.

[0017]In one approach, the fine tracking system includes an adaptive optics loop that is driven by the reflected light. For example, the adaptive optics loop can include a deformable mirror, a wavefront sensor and a controller. The wavefront sensor senses the wavefront of the reflected light and a controller drives the deformable mirror based on the sensed wavefront. The deformable mirror corrects the incoming wavefront, thus steering the camera to the eye (i.e., correction of tip and tilt wavefront errors). The deformable mirror may also focus the camera (i.e., correction of focus-error). In this way, the image capture subsystem can acquire iris images, even without the subject's active cooperation.

[0018]The iris imaging system may also include an acquisition subsystem that identifies the approximate location of subjects within a capture volume. For example, a wide field of view acquisition subsystem may be coupled with a narrower field of view image capture subsystem. The acquisition subsystem identifies the approximate location of subjects, and the image capture subsystem slews from one subject to the next to acquire images of their irises. A controller coordinates the two subsystems. In one approach, the acquisition subsystem identifies the approximate location of subjects based on retro-reflections from the subjects' eyes. This is convenient since the circular shape of the eye pupil allows one to easily distinguish retro-reflections from the eye from other light sources.

Problems solved by technology

The image capture subsystem captures images of irises, possibly with resolution that is not sufficient for biometric identification.

Images